With the advent of more robust wireless communications systems, compatible handheld communication devices are becoming more prevalent, as well as advanced. Where in the past such handheld devices typically accommodated either voice (cell phones) or text transmission (pagers and PDAs), today's consumer often demands a combination device capable of performing both types of transmissions, including sending and receiving e-mail. The suppliers of such mobile communication devices and underlying service providers are anxious to meet these demands, but the combination of voice and textual messaging, as well as other functionalities such as those found in PDAs, have caused designers to have to improve the means by which information is input into the devices by the user, as well as provide better facilitation for the user to navigate within the menus and icon presentations necessary for efficient user interface with these more complicated devices.
For many reasons, screen icons are often utilized in such handheld communication devices as a way to allow users to make feature and/or function selections. Among other reasons, users are accustomed to such icon representations for function selection. A prime example is the personal computer “desktop” presented by Microsoft's Windows® operating system. Because of the penetration of such programs into the user markets, most electronics users are familiar with what has basically become a convention of icon-based functionality selections. Even with many icons presented on a personal computer's “desktop”, however, user navigation and selection among the different icons is easily accomplished utilizing a conventional mouse and employing the point-and-click methodology. The absence of such a mouse from these handheld wireless communication devices, however, has necessitated that mouse substitutes be developed for navigational purposes. Mouse-type functionalities are needed for navigating and selecting screen icons, for navigating and selecting menu choices in “drop down” type menus and also for just moving a “pointer” type cursor across the display screen.
Typically, handheld electronic devices have been provided with a navigation tool for movement among the several available menus. The navigation tool also typically has the ability to direct the cursor movement on the screen of the device or scroll through a page viewed on the device.
Today, such mouse substitutes take the form of rotatable thumb wheels, joysticks, touchpads, four-way cursors and the like. In the present description, a trackball is also disclosed as a screen navigational tool. Since the trackball freely rotates within a receiving socket, the user is able to control the rate of rotation and desired direction of rotation of the trackball. This ability provides the user with a different feel for navigation within programs as compared to other navigational devices. This behavior creates an increased need for varying sensitivity; i.e., the amount of cursor movement induced by a particular amount of movement of the rollerball. For example, the range of motion of the cursor to navigate between icons on a home screen is much less than the range of motion required in scrolling through a lengthy email message.